PrePoMax (CalculiX FEA) - Tutorial 20 - Hex mesh from Gmsh

PrePoMax is an open-source pre- and postprocessor for (also open-source) finite element analysis solver CalculiX. It's extremely user friendly and doesn't even require installation. PrePoMax can be used only on Windows.
In this tutorial I would like to show you how to create a hexahedral mesh in Gmsh (another open-source software) and import it for use in PrePoMax.
Geometry in step format: drive.google.com/file/d/1dsTT...
PrePoMax homepage: prepomax.fs.um.si/
Gmsh homepage: gmsh.info/

[@Toni-yl4hc]

Great tutorial 👏🏻👏🏻👏🏻. I think creating more detailed meshes would be interesting to know to improve Prepromax results.

[@Panvil]

Hey. I think it would be super interesting if you did more of these hexa mesh tutorials, I've previously used Salome-Meca for that a bit, but i'm interested in learning Gmsh too. Great tutorial as usual

[@FEAnalyst]

To be honest, I’m not very experienced with Gmsh. I was rather thinking about making a tutorial with hex mesh generated in Salome_Meca. But I will think about showing Gmsh again. There aren’t many tutorials for this software (and the best ones are in German) and it’s not very user-friendly so I guess that additional videos covering Gmsh could be useful.

[@Panvil]

@@FEAnalyst do you prefer salome-meca over gmsh? I'm on the lookout for a good open source hex mesher, and I think salome meca is actually pretty good for that

[@FEAnalyst]

@@Panvil Both are quite unintuitive but in different ways. Salome_Meca has strange GUI where you have to go through lots of steps to do anything and there are some unnecessarily complicated meshing procedures (like having to select from some algorithms and their rules with not so descriptive names). Gmsh has simpler GUI but because of that meshing is less automated and requires getting familiar with scripting commands. Also, it seems that Salome_Meca has more advanced hex meshing algorithms and Gmsh specializes more in tetrahedral meshes. However, these two programs are the only open-source hex meshers so there’s no other choice. All in all, I think that I would use Gmsh for simpler cases and Salome_Meca for more complex ones. But this preference may change once I get more familiar with both tools.

[@tiborkemeny8644]

@@Panvil Salome is strange, I admit it and it needs a lot of practice (I've been doing it for a while and I still have problems, so carry on :) )

[@esarworks4963]

@@FEAnalyst There is always cgx the native tool for Calculix. But if you are looking for something intuitive run as far away as you can from it. In 2010 cgx, Netgen and Gmsh were the only decent options available. I have some documentation on cgx if anyone is interested. cgx can handle all Calculix element types since its written specifically for that solver.

[@tiborkemeny8644]

Great tutorial.
For me using Salome-Meca seems easier than Gmsh for some tricky geometry (I made some Nozzle-Shell and Nozzle Head calculation with Salome/Prepomax)

[@FEAnalyst]

Thanks, I can also prepare a version of this tutorial with Salome-Meca.

[@tiborkemeny8644]

@@FEAnalyst this is my personal opinion, but for head/nozzle connection the Salome's i,j,k-method is the best hexameshing solver - in the OS scene.
Yes, sometimes the geometry gives some hard time, but slicing the surfaces could help a lot. For me the GUI of Gmsh is to strange.
The only reason why I haven't kicked out the win-system is Prepomax. To handle Salome is a little bit difficult too. Combine the 2 systems together is my personal favorite in the FEA field.

[@FEAnalyst]

@@tiborkemeny8644 By the way, do you know if Salome_Meca’s source code is available somewhere ? I couldn’t find it so far (I’ve only found the source code of code_aster solver).
Unfortunately, there are just a few non-commercial meshers capable of generating hex meshes and I also have the impression that Salome-Meca is the most advanced of them, offering various techniques (including hexa block) for generation of complex meshes. It’s not user-friendly but really powerful (just like the aforementioned code_aster solver). One more interesting free hexa mesher is IA-FEMesh but it’s limited to hexa block technique and designed for quite specific applications (models obtained from medical imaging). Apart from these three, there’s pretty much no other non-commercial solution. Well, theoretically, there’s also the SnappyHexMesh associated with OpenFOAM but I don’t know if it makes sense for structural models.

[@tiborkemeny8644]

@@FEAnalyst I haven't find it either. My first guess will be the salome for windows community. They should have something...

[@FEAnalyst]

@@tiborkemeny8644 From what I've found, source code of Salome_Meca is available for its Linux version. However, the Windows port is built by a company that provides only the binaries.

[@TheBabias]

Thank you for these amazing tutorials! Do you know if there is a pre processor that can make mesh quality checks?

[@FEAnalyst]

Some mesh quality checks are available in Gmsh and Salome. Here’s a discussion about this on CalculiX’s forum: calculix.discourse.group/t/mesh-quality-check/743

[@TheBabias]

@@FEAnalyst Thank you very much for your reply!

[@esarworks4963]

Yes ! cgx can check element quality. Haven't used it for a long time, just getting back to simulations.